1. Field of the Invention
The present invention relates to a controller of an ejector mechanism for ejecting a molded product from a mold in an injection molding machine, and also to a method of setting a terminal position of a forward motion of ejector pins of the ejector mechanism.
2. Description of Related Art
In an injection molding machine, after resin is injected into a mold and concreted, the mold is opened and a molded product in the mold is ejected by an ejector mechanism. The ejector mechanism ejects a molded product by moving ejector pins forward to project into a cavity of the mold against an elastic force of return springs for returning the ejector pins to a retracted position. A pneumatic cylinder, a linear motor or a servomotor may be employed as a driving source for moving the ejector pins forward. A brake device is used for generating a retaining force to retain the ejector pins at a terminal position of the forward motion against the elastic force of the springs (see JP10-296818A, for example).
Since the brake device retains the ejector pins at the terminal position against the elastic force of the springs by the retaining force, the retaining force has to be greater than the elastic force of the springs at the terminal position of the forward motion of the ejector pins. If the elastic force of the springs is greater than the retaining force of the brake device in a state where the ejector pins are retained at the terminal position, friction members for generating braking force, such as a brake shoe and a brake band of the brake device are excessively worn to make a cause of malfunction of the brake device.